Combination apex and side seals for rotary piston engines

ABSTRACT

A combination apex corner seal and side compression seal for rotary piston internal combustion engines, the combination consisting of wishbone shaped members having two legs diverging from an integral hub, the hub being shaped to form the end member of an apex seal, the legs of the wishbone indexing with grooves in the side of the piston and forming side compression seals.

United States Patent [1 1- McCormick Oct. 30, 1973 [54] COMBINATION APEXAND SIDE SEALS 3,033,180 5/1962 Bentele 418/123 X O ROTARY PISTONENGINES 3,194,488 7/1964 Fuhrmann 418/113 3,309,011 3/1967 Osakada eta1. 418/61 X Inventor: Harold E. McCormick, Ballwin, Mo.

Assignee:

Filed: Oct. 27, 1971 Appl. No.:. 193,059

US. CLL 418/142, 418/113 Int. Cl. F0lc 19/08 Field of Search 418/61,143,.144,

References Cited UNITED STATES PATENTS Wankel et a] 418/120 X Bentele418/121 Ramsey Corporation, St. Louis, Mo.

Primary ExaminerCarlton R. Croyle Assistant ExaminerMichael Koczo, Jr.AttorneyCarlt0n Hill et a1.

[57] ABSTRACT A combinationapex corner seal and side compression sealfor rotary piston internal combustion engines, the combinationconsisting of wishbone shaped members having twolegs diverging from anintegral hub, the hub being shaped to form the end member of an apexseal, the legs of the wishbone indexing with grooves in I the side ofthe piston and forming side compression seals.

19 Claims, 11 Drawing Figures Patented Oct. 30,1913 I 3,768,936

2 Sheets-Sheet 1 I INVENTOR. hkzup f M: [bkM/CK BY ATTORNEYS PatentedOct. 30, 1973 3,768,936

' 2 Sheets-Sheet 2 v 71. ma ATTORNEYS COMBINATION APEX AND SIDE SEALSFOR ROTARY PISTON ENGINES BACKGROUND OF THE INVENTION 1. Field of theInvention This invention relates to the internal combustion engines andmore particularly to compression and apex seals for rotary pistonengines.

2,. Description of the Prior Art v Rotary piston engines, particularly.of the Wankel type, utilize a rotating piston or rotor having axial endwalls and a variously dimensioned periphery having thereon corners atthe apexes of the sides of the periphery. .In order to separate thesides from one another when the rotor is received in the chamber, apexseals are used at the intersections of the peripheral sides to sealagainst the wall of the chamber. Further, the rotor is received betweentwo non-rotating end plates and side seals are necessary to preventfluid flow between the chamber cavity radially outward of the rotor andthe central opening in the rotor. In order to reduce such leakage to aminimum it is desirable that the side seals be placed as close to theperiphery as possible. Heretofore, the prior art has provided grooves inthe periphery extending along the line of the apex for receipt of theapex seal. These grooves have extended from side to side of the rotorand have intersected thereat with grooves in the side walls of the rotorextending between the ends of the apex grooves. The side grooves receivecompression seals which are spring urged axially outwardly. The point ofintersection between the side seals and the apex seals presents amechanically difficult sealing point. Part of the mechanical difficultyarises from the fact that the apex seals must be urged radiallyoutwardly in contact with the surface of the rotor chamber while theends of the apex seal need to be sealed against side leakage betweentheir ends and the end plates. This requires an axially expansive force.A typical method of solving the problem, as used in the prior art,required the provision of counterbores in the axial ends of the apexseal groove,

SUMMARY OF THE INVENTION My invention overcomes the disadvantages of theprior artin that it provides a combination side seal and apex cornerseal. The invention, in its preferred embodiment, makes use of a widerside seal, allowing the use of a wider groove, thereby eliminating theneed for complex machining of the rotor. Additionally, because I havecombined the apex corner seal and the combustion seals into one piece,the problem of sealing at the intersection between the side seal and theapex seal is eliminated.

My invention also provides a novel apex seal construction consisting ofa cylindrical member interposed between two of the corner seal portionsof the combination and indexed therewith. The cylindrical member 1 has aconfiguration allowing receipt of the apex seal.

the counterbores receiving corner seal members which 7 In typical priorart embodiments, two or more side I seals were provided, requiring twoor more grooves extending between the apex seal grooves. Linearly curvedseals were received in the grooves and had their ends abutting cornerseals received in the apex grooves. This required a clearance betweenthe compression seal on the side and the corner seal to compensate forexpansion as well as to allow easy installation.

Further, the corner seal and apex seal required a multipiececonstruction wherein the corner seal comprised The seals of thisinvention are specifically illustrated for use in connection with athree-sided rotor of the type normally used in a trichoid chamber of arotary combustion engine such as a Wankel engine. The rotor is formedwith grooves at the three apexes and with side grooves extending betweenthe ends of the apex grooves in close spaced relation to the peripheryof the rotor. Three of the combination apex and side seals are used oneach side of the rotor with a portion of the seal received in the.groove of the apex and with legs depending therefrom received in theside grooves. The legs terminate in stepped portions which index with aleg of the adjacent combination seal intermediate the apexes. The legsmay be spring backed in the grooves.

Preferably the legs have a longitudinally extending groove intermediatethe side thereof, the groove providing for distribution of lubricatingoil in' the rotor chamber.

In the preferred embodiment the combination seals are 'formed of apolyimide material. This material may be filled with graphite ifdesired. The use of the polyimide material aids in elimination ofcompression seal sticking in the grooves, which problem has been commonto the prior art. The use of theugraphite further aids in theelimination of side sticking, while also reducing the coefficient tofriction between the seal and the end plate and adding to the life spanof the seal.

It is therefore an object of this invention to provide a new method ofsealing for rotary piston engines.

' It is a further object of this invention to reduce the number ofcomponents necessary for sealing the rotor of a rotary piston combustionengine.

It is another object of this invention to provide side and apex sealsfor the rotor of a rotary piston engine which is capable of beinginstalled'by automatic machinery.

It is a further object of this invention to reduce the complexity ofinstallation of side and apex seals in roa multiplicity of partsincluding expander members'etc.

tary engines.

It is another and specific object of this invention to provide acombination apex corner seal and combustion side seal for rotary pistonengines.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantagesof the invention will be readily apparent from the following descriptionof certain preferred embodiments thereof, taken in conjunction with theaccompanying drawings, although variations and modifications may beeffected 3 without departing from the spirit and scope of the novelconcepts of the disclosure, and in which:

FIG. 1 is an exploded perspective view of a rotor equipped with theseals of this invention.

FIG. 2 is a side plan view of a rotary piston engine rotor received in atrochoid chamber.

FIG. 3 is a fragmentary cross sectional view of one of the side seallegs of the seal of this invention received in a ring groove in therotor.

FIG. 4 is an end plan view of the expander spring this invention.

F lg. 5 is a fragmentary plan view taken along the lines V--V of FIG. 4.

FIG. 6 is a fragmentary side plan view of one embodiment of thecombination corner and combustion seal of this invention.

FIG. 7 is a top plan view of the seal of FIG. 6.

FIG. 8 is a top plan view of a pair of seals according to FIGS. 6 and 7,equipped with the apex seal receiving member'of this invention.

FIG. 9 is a fragmentary end plan view of the device of FIG. 8 takenalong the lines IXIX of FIG. 8.

FIG.*10 is a view similar to FIG. 8 illustrating a modification thereof.

FIG. 1 l is a view similar to FIG. 6 illustrating another modificationof the combination corner and side seal of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explodedperspective view ofa rotary piston internal combustion engine rotor 10.The-rotor has three sides around its outer periphery, each of the sidesbeing curved and meeting the adjacent side at an apex point 12. An axialgroove 13 is formed into the body of the rotor at each of the apexes andextends from axial side to axial side of the rotor.

As illustrated in FIG. 2, each of the apex grooves contains an apex seal14 which projects therefrom into contact with the inner surface 15 ofthe trochoid shaped piston chamber 16.

In each of the side walls 17 of the rotor, three grooves 18 are formed.The grooves extend axially into the rotor 10. Eech of the groovesextends from the end of one apex groove 13 to the end of another groove13 and each of the grooves 18 is opened at its longitudinal end to thecorresponding apex groove 13.

The grooves 18 receive compression seals which are urged into contactwith the end plates closing the trochoid housing. In this manner theapex seals 14 seal the periphery of the housing dividing the housinginto a number of moving chambers while the compression sealsseal'against the end plates thereby effectively sealing each of thethree volume changing chambers 19,19a and 19b defined between theperiphery of the rotor 10 and the inner surface of the.trochoid. Thecompression seals are necessary to prevent leakage from the chambers 19along the side of the rotor between the side walls 17 and the end platesto the open center 20 of the rotor. Additionally because some areas ofthe rotor chamber are always under high pressure whereas other areas arealways under low pressure, the compression seals 21 which are receivedin the grooves 18 prevent sideways leakage from the high pressure areasto the low pressure areas.

In order to reduce the cavity at the sides of the rotor outward from thecompression seals 21, the seal difficulty was encountered in sealing atthe corner or intersection between the apex groove and the compressionseal groove. Further, the compression grooves were normally narrow anddeep on account of which the grooves were difficult to machine.

The normal manner of achieving a sealat the corner was to abut thelongitudinal ends of the compression seals against a corner seal, whichseal wasnor'mally independent from the apex seal and which in turn had agroove receiving the apex seal. In order to provide for expansion of theseals, a clearance fit relation was required between the compressionseals and corner seal. This allowed for leakage paths. Further, thecomplex nature of the seal required numerous parts including expandersand the like. In some embodiments as many as 36 parts per rotor wererequired just for the compression and corner seals and not including theapex and oil seals. Assembly and installation were therefore extremelyexpensive and time consuming.

My invention provides for a combustion corner and compression seal whichovercomes all of the disadvantages of the prior art. First, the grooves18 are considerably wider than prior art grooves, thereby reducing themachining expense. The grooves 18 receive expander srpings 22 andcombination corner and compression seal members 23. Thecombinationcorner and compression seal members, as illustrated in FIG. 1, aresubstantially wishbone shaped. That is to say that they have a commonhub 25 representing the corner seal. Projecting a V-shaped angle fromthe hub are two compression seal portions 26.The compression sealportions 26 are integral with the hub 25. Each of the compression sealsections terminates in a stepped end 27 which is indexable with thestepped end 27 of an adjacent compression seal section.

Three such seal members are used per rotor side, each of the sealmembers having its hub 25 received at the longitudinal end of the apexseal'groove l3 and the compression seal leg portions 26 received in thegrooves 18 diverging from the apex groove 13. The legs or compressionseal portions 26 are dimensioned to extend approximately half of thedistance of the grooves 18 from one apex 12 to the next. At the point oftermination, they interfit with the stepped end portion 7 of the member23 used in connection with the next apex 12.

It is to be understood that, if desired, the legs of a given member maybe of unequal length. One reason for doing this can be for accommodatingport placement in'the end plates.

The compression seals are backed by the springs 22. One spring isreceived in each groove 18 and backs the compression seal portions 26 ofthe two adjacent seal members 23.

Apex seals such as the seals 14 or the seals 30 illustrated in FIG. 1are received in apex spacers 31 which are received in each of the apexgrooves 13. The spacers interfit with the hub portions 25 in a mannerwhich either allows the spacer 31 to rotate in the groove 13 to providea swinging apex seal or which is restrained against rotation for use inconnection with non-' swinging type seals. I

I As best illustrated in FIG. 3, each of the leg portions 26 has acentral groove 32 running for most of the length of the leg portions 26.The central groove may be closed at both the hub and the stepped end 27.The groove 32 has the function of carrying lubricant for sealing andwear purposes. The groove is centrally located transversely of the sealproviding a raised land 33 to either side of the groove.

The reverse side, or backside 34 of the leg members, in the preferredembodiment, is centrally reduced in radial width providing two ledges 35and 36 with a central projecting portion 37 extending behind the ledges.

If desired, the bottom or inside edge 38 of the leg portions may betapered as'illustrated at 39.

The spring member 22 is best illustrated in FIG. 4, being substantiallyU-shaped in cross section having inner 40 and outer 41 diameter legsinterconnected at one axial end thereof by a bight section 42. The freeaxial ends 43 of the legs 40 and 41 abut the ledges 35 and 36. Thespring 22 is preferably formed of spring metal and has struck-outportions 47 and 48 formed from portions of the legs 40 and 41 and thecorresponding bight portions. The portions 47 and 48 extend beyond theback 49 of the bight section 42 and are adapted to be springinglydeformed from their normal position illustrated in FIG. 4 to theposition illustrated in FIG. 3. In this manner, they bottom against theback wall 50 of the grooves 18 and by their spring resiliency urge thespring member 22 away from the back wall 50. This urging of the springmember is transmitted through the ledges 35, 36 to the compressionseals, thereby urging the compression seals partially out of the ringgroove 18 and into contact with the end plates.

It is desirable not only to seal against the end plates but also to sealagainst one wall of the groove. Normally this is best accomplished bysealing against the innermost side wall of the groove 52. For thispurpose, portions 53 of the outer leg 41 are punched out in the mannerof a tab from the material of the outer diameter leg, asbest'illustrated in FIGS. 4 and 5. The portions 53 are preferably bentand are resilient due to the spring nature of the material of the ring.These portions 53 abut the outer side walls 54 of the groove 18 asillustrated at 55 in FIG. 3. This urges the spring 22 and consequentlythe compression seal 26 against the opposite side wall 52 providing aseal between a portion of the bottom side 58 of the compression seal andthe side wall 52 of the ring groove. This seal is aided by the pressureof gases trapped in the chambers'l9, 19a and 19b which may gain accessto the groove 18 at the top corner 59 thereof from the space between thesides of the rotor and the end plates. This pressure is entrapped in thering groove because of the seal point 58 and aids in urging thecompression ring out of the groove into tighter contact with the endplate.

The spring also is capable of holding the combination apex corner andcompression seal membersin a unitary assembly. That is .tosay thatthespring member can be pre-attached to the three wishbone shaped sealsprior to the assembly into the groovesin the engine and will thereaftermaintain the wishbone units in assembledtogether relation, allowinginstallation by automatic machinery.

The hub portions 25 of the seal members 23 may be configureddifferently. FIGS. 6 through 9 and FIGS. 10

and 11 illustrate alternative embodiments. In FIGS. 6 through 9, the hubportion is configured to receive an apex spacer in a manner which willallow the spacer to pivot within the hub portion. FIGS. 10 and 1 1illustrate a non-pivoting configuration.

Basically, as illustrated in FIG. 1 and in FIGS. 8 and 9, the hubportion 25 is wider than the compression seal portion 26 of the member23. The hub portion is semi-cylindrical having an arcuate portion60which depends below the connecting point 61 between the hub portion andthe undersides of the compression seal portions 26. The hub portion isalso curved beyond the outer side of the seal portions. The apex grooves13 are preferably cylindrical and open to the exterior along a line. Thehub portions 25 are receivable in the cylindrical apex grooves. Theoutside face 62 of the hub portion is substantially planar with theoutside faces 33 of the compression seal while the inside face 63extends beyond the inside face 34 of the compression seal member.Because the outside face 62 is flush with the sealing surfaces 33 of thecompression seals, the hub serves as a corner seal at the intersectionbetween the compression seal grooves and the apex seal groove. The factthat the hubs are insertable into the axial ends of the apex seal groove13 blocks those ends and seals against the end plates.

The hub portions 25 have grooves therein. In the embodiment illustratedin FIGS. 6-through 9, the grooves 65 have curved bottoms 66 and are opento the top of the seal member, the top being definable as that point ofthe cylindrical body most remote from the point of projection of thecompression seal legs. The opening is dimensioned to receive the ends ofthe apex spacer. The apex spacer, as illustrated in FIG. 8, is acylindrical member 70 having reduced diameter end portions 71 with aconstant diameter central portion 72. A groove 73 extends axially of thespacer and is open to the periphery thereof, the groove extending intothe spacer approximately half of its diameter.

The spacer has an axial dimension approximately equal to the width ofthe rotor whereby its axial ends 74 and 75, when received in the groove65 of the sealing member 23, will be flush'with the axial ends of therotor. If desired, the apex spacer may be shorter than the operatingdistances between opposed sealing surfaces 33 of opposed sealing members23, the apex seal then being formed by the bottom wall 66 of the groove65 and the outer face 62 of the hub member. The diameter reduction ofthe end portions 71 is dimensioned axially andradially so as to allowreceipt of the axial ends 71 within the grooves 65 of the hub portions25 in the manner illustrated in FIG. 8. If desired, the diam eter of theend portion 71 may be slightly larger than the dimension of the openingof the groove 65 so that the apex spacer is snapped thereinto. Thegroove 73 of the spacer receives the apex seal. The embodimentillustrated in FIGS. 6 through 9 is designed to receive a seal snuglywithin the groove 73 in a nonpivotal relation therein. The spacer 72,however, is pivotable in the hubs 25 of opposed sealing members 23 toprovide for pivotability of the apex seal against the surface 15 of therotor chamber. The diameter of the central portion 72 of the apex spacerissubstantially equal to the diameter of the grooves 13 and of the hubs25 whereby the spacer and hubs will be snugly received in the grooves toreduce pressure escape paths. Of course, it is to be understood that thecurvature of the cylindrical section of the hub 25 and of the spacer 70is dimensioned with respect to the curvature of the grooves 13 and thatif the grooves 13 are not cylindrical, then the hub and spacerconfiguration will be equally non-cylindrical in this embodiment.

It should further be understood that although the groove 65 of the hubhas been described as being open at both axial ends thereof, in amodified form, the groove could be closed at the outer axial end whichcontacts the end plate. In such an instance, the closure of the groovewill act as a further seal. Further, if it is desired to use the spacer70 in a non-pivotal embodi ment, then the grooves 13 of the rotor andthe corresponding exterior surfaces of the hub 25 and of the spacer 70can be configured to prevent rotation in the groove. It will be furtherappreciated that the hubs and spacer are not locked together axially andthe spacers are axially movable with respect to the hub so as to allowaxial expansion of the combination corner seal and compression sealmembers.

FIGS. and 1 1 illustrate a modified form of the hub configurationtogether with a modification of the apex spacer. This configuration isdesigned to prevent twisting or rotation of the apex spacer with respectto the hubs. The embodiments of FIGS. 6 through 9 allowed such movementof the spacer with respect to the hubs.

In the embodiment illustrated in FIG. 10 and illustrated in FIG. 1, thehub 25 has a narrower groove 80 than the previous embodiment. Further,the hub has a reduced diameter extension 81 projecting from the insideend 82 of the main hub section. The reduced diameter portion has a pairof opposed full diameter sections 83 which provide locking nibs 84. Thespacer has a groove 85 substantially the same width as the groove 80 ofthe hubs. Further, the axial ends 86 of the spacer terminate with acentral cavity 87 dimensioned to receive the reduced diameter end 81 ofthe hubs therein. The peripheral portion 88 around the cavities 87 has apair of slots 89 therein. The slots are aligned with the tabs 84 anddimensioned to receive the tabs. Thus,.when the spacer is fitted overthe reduced diameter end 81 of the hubs, with the reduced diametersection extending into the cavity 87, the tabs 84 will interfit with theslots 89 thereby locking the spacer against rotation with respect to thehubs. In'this embodiment, the spacer has an axial length sufficient toextend from one hub to the opposed hub at one apex and to substantiallyfill the apex groove 13. The spacer terminates at the interfit with thehubs rather than extending to a point adjacent the sides of the rotor asis the case with the embodiment of FIGS. 6 through 9. It is to beappreciated that the grooves 80, 85 illustrated in the embodiments ofFIGS. 10 and 11 are substantially wider than the grooves 73 of thespacer 70 of FIG. 8. This is to allow receipt in the spacer of a wideror of a pivotable apex seal. However, the grooves could be of differentdimensions depending upon the apex seal which they are to be used with.

In the preferred embodiment, the combination corner and compression sealas well as the apex spacer are composed of high-temperature resistingplastic material such as polyimide resins filled or intermixed withgraphite or metallic materials. In a preferred embodi ment, some of thefiller is in fibrous form graphite fibers being used in an amount ofabout percent by weight, particulate graphite in about the same amountand the remainder polyimide resin.

It will therefore be seen from the above that my invention provides aunique combination corner and compression seal for rotary pistonengines. The seal combination, as illustrated, consists of threewishboneshaped seal members, each of which has a hub section receivablein the apex seal groove and two depending leg sections which comprisethe compression seals and which are received in compression seal grooveson the sides of the rotor. The legs terminate in stepped configurationsallowing overlapping of adjacent legs from adjacent combination members.Also illustrated and disclosed is a configuration of the leg memberswhich has a central projection which can be enclamped by the legs of adisclosed spring member allowing preassembly of the entire systemproviding a unit which is easily insertable into the rotor by automatedmachinery. Further disclosed is a method of assuring side sealingbetween the compression seal legs and the side walls of the groove inwhich they are received and various designs and construction features ofhubs and interfitting apex spacers for receipt in the apex groove, thecombination of hubs and apex spacers allowing either swinging movementof an apex seal and spacer with respect to the hubs or a locking of thespacer against such movement. Because of the integral construction ofthe hubs and legs, the heretofore described difficulties of sealing atthe intersection between the compression seals and the apex grooves onrotary piston engines has been substantially eliminated.

Although the teachings of my invention have herein been discussed withreference to specific theories and embodiments and although illustrativemeans for accomplishing explained results have been described, it is tobe understood that these are by way of illustration only and that othersmay wish to utilize my invention in different designs or applications.

I claim as my invention:

1. In a rotary piston engine with the rotor received between end plates,the rotor having apex periphery seals and side compression seals, theapex seals received in apex grooves and the compression seals receivedin side wall grooves, the improvement of a combination compression sealand apex corner seal member, the compression seal havinga length andcontacting an adjacent end plate along substantially'its entire length.

2. The improvement of claim 1 wherein the combination is substantiallywishbone-shaped having a hub adapted to be received in the apex grooveand two depending leg members integral with said hub divergingtherefrom, the said leg members comprising compression seals and adaptedto be received at least partially in the side grooves. I

3. A combination corner seal and compression seal fo use in rotarypiston engines comprising a wishboneshaped member having a hub portionwith a pair of integral diverging compression seal legs projecting fromthe hub portion, the combination having coplanar sealing faces alongsubstantially the entire surface of one side thereof.

4. The combination of claim 3 wherein the said legs have front and backsides, the said front sides providing sealing surfaces for engagementwith an end plate closing a rotary piston chamber.

5. The combination of claim 4 wherein the hub por tion has a front and aback surface, the front surface planar with the sealing surface of thelegs and the back surface projecting beyond the back surface of thelegs.

6. The combination of claim 4 wherein the sealing surface of the legshas a central groove therein.

7. A sealing assembly for rotary pistons, the rotor having apex groovesand side wall compression seal grooves, the ends of the side wallcompression grooves intersecting the axial ends of the apex grooves, theassembly comprising a plurality of sealing members, each of said sealingmembers having corner seal-forming portion dimensioned to be snuglyreceived in the end of an apex seal groove, each of said members havingtwo compression seal portions, integral with the corner seal portion,the compression seal portions dimensioned to be received in thecompression seal grooves which project from and intersect with the apexgroove in which the corner seal portion is received, the compressionseal portions and corner seal-forming portion having sealing surfacesthereon adapted to be pressed into sealing relation with the wall of anend plate positioned adjacent the rotor.

8. The assembly of claim 7 including spring means received in saidcompression seal grooves, said spring means effective to resilientlyaxially bias the said compression seal portions out of the saidcompression seal grooves.

9. The assembly of claim 8 wherein the said spring means is effective toresiliently bias the compression seal portions against a side wall ofthe compression seal groove in sealing relation therewith.

10. The assembly of claim 7 wherein two corner seal forming portions areprovided for each apex groove, one of said portions received in each endof the apex groove and anapex spacer is provided in the said apex groovespanning the distance between the corner seal portions.

11. The assembly of claim 10 wherein the said apex spacer has axial endportion indexing with portions of the corner seal portions.

12. The assembly of claim 11 wherein the apex spacer is pivotable withrespect to corner seal portions.

13. The assembly of claim 11 wherein the apex spacer is prevented frompivoting with respect to the corner seal portions.

14. The assembly of claim 7 wherein the sealing members are formed of aplastic.

15. The assembly of claim 14 wherein the plastic is a polyimide.

16. The assembly of claim 15 wherein the polyimide is graphite filled.

17. The assembly of claim 7 wherein the compression seal portions haveend surfaces shaped to mate with end surfaces of an adjacent compressionseal.

18. The assembly of claim 17 wherein the mating end surfaces form aseal.

19. The assembly of claim 8 wherein the spring means embraces portionsof adjacent sealing members to hold the assembly together as a unit.

1. In a rotary piston engine with the rotor received between end plates,the rotor having apex periphery seals and side compression seals, theapex seals received in apex grooves and the compression seals receivedin side wall grooves, the improvement of a combination compression sealand apex corner seal member, the compression seal having a length andcontacting an adjacent end plate along substantially its entire length.2. The improvement of claim 1 wherein the combination is substantiallywishbone-shaped having a hub adapted to be received in the apex grooveand two depending leg members integral with said hub divergingtherefrom, the said leg members comprising compression seals and adaptedto be received at least partially in the side grooves.
 3. A combinationcorner seal and compression seal for use in rotary piston enginescomprising a wishbone-shaped member having a hub portion with a pair ofintegral diverging compression seal legs projecting from the hubportion, the combination having coplanar sealing faces alongsubstantially the entire surface of one side thereof.
 4. The combinationof claim 3 wherein the said legs have front and back sides, the saidfront sides providing sealing surfaces for engagement with an end plateclosing a rOtary piston chamber.
 5. The combination of claim 4 whereinthe hub portion has a front and a back surface, the front surface planarwith the sealing surface of the legs and the back surface projectingbeyond the back surface of the legs.
 6. The combination of claim 4wherein the sealing surface of the legs has a central groove therein. 7.A sealing assembly for rotary pistons, the rotor having apex grooves andside wall compression seal grooves, the ends of the side wallcompression grooves intersecting the axial ends of the apex grooves, theassembly comprising a plurality of sealing members, each of said sealingmembers having corner seal-forming portion dimensioned to be snuglyreceived in the end of an apex seal groove, each of said members havingtwo compression seal portions, integral with the corner seal portion,the compression seal portions dimensioned to be received in thecompression seal grooves which project from and intersect with the apexgroove in which the corner seal portion is received, the compressionseal portions and corner seal-forming portion having sealing surfacesthereon adapted to be pressed into sealing relation with the wall of anend plate positioned adjacent the rotor.
 8. The assembly of claim 7including spring means received in said compression seal grooves, saidspring means effective to resiliently axially bias the said compressionseal portions out of the said compression seal grooves.
 9. The assemblyof claim 8 wherein the said spring means is effective to resilientlybias the compression seal portions against a side wall of thecompression seal groove in sealing relation therewith.
 10. The assemblyof claim 7 wherein two corner seal forming portions are provided foreach apex groove, one of said portions received in each end of the apexgroove and an apex spacer is provided in the said apex groove spanningthe distance between the corner seal portions.
 11. The assembly of claim10 wherein the said apex spacer has axial end portions indexing withportions of the corner seal portions.
 12. The assembly of claim 11wherein the apex spacer is pivotable with respect to corner sealportions.
 13. The assembly of claim 11 wherein the apex spacer isprevented from pivoting with respect to the corner seal portions. 14.The assembly of claim 7 wherein the sealing members are formed of aplastic.
 15. The assembly of claim 14 wherein the plastic is apolyimide.
 16. The assembly of claim 15 wherein the polyimide isgraphite filled.
 17. The assembly of claim 7 wherein the compressionseal portions have end surfaces shaped to mate with end surfaces of anadjacent compression seal.
 18. The assembly of claim 17 wherein themating end surfaces form a seal.
 19. The assembly of claim 8 wherein thespring means embraces portions of adjacent sealing members to hold theassembly together as a unit.